Regolith as Baseline to a Future Space Farm

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Biodegradable mulching vs traditional polyethylene film for sustainable solarization: Chemical properties and microbial community response to soil management

Abstract Soil solarization is usually performed with polyethylene plastic films, which are often disposed of by taking them to landfills, burying them in soil, burning them or occasionally recycling them, and these approaches have a great impact on the environment. Therefore, the use of biodegradable films seems to be an interesting eco-sustainable alternative to traditional films. The effect of soil solarization carried out by using biodegradable mulch or traditional polyethylene plastic film was determined under greenhouse conditions. The response of the soil was assessed by chemical determinations and microbiological culture-dependent and culture-independent approaches to evaluate the microbial biodiversity, biological status and quality of the soil. The biodegradable film avoided a high ammonia concentration in the soil, thanks to both lower soil water content and slightly lower temperature than polyethylene film, and these conditions probably have been optimal for growth of nitrifying bacteria, which were more efficient in BIO, as highlighted not only by lower ammonia value but also by higher nitrate value. Both films did not affect organic matter and total nitrogen content. Moreover, the modifications of the environmental and ecological conditions associated with the different film covers applied to the soils affected prokaryotic and eukaryotic populations, leading to the establishment of a new dominant microbial community. Interestingly, microbiological analyses highlighted a different behavior modulated with the two films indicating different times of recovery post stress. Overall, the results highlighted the potential of biodegradable film that appears to be a suitable replacement for traditional polyethylene plastic film for soil solarization, with great environmental benefits

Nutrient Solution Deprivation as a Tool to Improve Hydroponics Sustainability: Yield, Physiological, and Qualitative Response of Lettuce

Hydroponics growing systems often contain excessive nutrients (especially nitrates), which could lead to a quality loss in ready-to-eat leafy vegetables and posing a health risk to consumers, if managed inadequately. A floating raft system was adopted to assay the production and quality performance of lettuce (Lactuca sativa L. cv ‘Maravilla De Verano Canasta’) deprived of the nutrient solution by replacement with only water, three and six days before harvest. Yield and quality parameters, mineral composition, pigments, organic acids, amino acids profile, soluble proteins, and carbohydrate content were determined. Nutrient solution deprivation six days before harvest resulted in a significant reduction in leaf nitrate (−53.3%) concomitant with 13.8% of yield loss, while plants deprived of nutrient solution three days before harvest increased total phenols content (32.5%) and total ascorbic acid (102.1%), antioxidant activity (82.7%), anthocyanins (7.9%), sucrose (38.9%), starch (19.5%), and γ-aminobutyric acid (GABA; 28.2%), with a yield reduction of 4.7%, compared to the control. Our results suggest that nutrient solution deprivation three days before harvest is a successful strategy to reduce nitrate content and increase the nutritional quality of lettuce grown in floating raft systems with negligible impact on yield. These promising results warrant further investigation of the potential effect of nutrient solution deprivation on the quality attributes of other leafy vegetables cultivated in floating raft systems and in a “cascade” growing system

In-Situ Resource Utilization (ISRU) for life support in Space

The 21st century is an era rich in scientific findings with rapid technological development. Hence space travels and the colonization of other celestial bodies would result no longer an image close to the world of science fiction but would be desirable soon. With this aim, many Space Agencies, Research Centers, and Universities are working to establish colonies self-sustaining. The establishment of such a complex system is expensive, in addition, it must be considered the commitment to planning and managing the replenishments, which makes it even more complicated. So, it is mandatory the costs reduction through the implementation of Bioregenerative Life Support Systems (BLSSs). The in situ resource utilization (ISRU) approach aims to reduce terrestrial input into a BLSS by using native regoliths and recycled organic waste as primary resources. A sustaining and auto-regenerating solution could be permanent agriculture, through the combination of BLSS and ISRU may allow sustainable food production on Moon and Mars, in a future long-term settlement. This research addresses this issue by seeking to improve the characteristics of extraterrestrial "soils" (regolith) and evaluating their effects on plants. Lunar and Martian regoliths are not available on Earth; therefore, space research studies are conducted on regolith simulants that replicate the physicochemical properties of extra-terrestrial regoliths. In our case, two simulants have been selected; one lunar (LHS-1) and one martian (MMS-1). Green compost and monogastric manure were involved in the experiments as surrogates of waste and excreta from the crew. To use as amendments to improve the simulants' characteristics. The lettuce (Lactuca sativa L.) was selected as a candidate crop to test, due to its agronomic and qualitative characteristics. Although the simulants can be a source of nutrients, it lacks organic matter, nitrogen, phosphorus and sulphur, which may be supplied by compost. So, in the first experiment, four different mixtures of Mars simulant and compost (0:100, 30:70, 70:30, and 100:0; v:v) were involved to assay the response of two butterhead lettuce (Lactuca sativa L. var. capitata) cultivars (green and red Salanova®) grown on, and physico-chemical and hydraulic properties of the different mixtures were evaluated. The experiment was performed in a phytotron open-gas-exchange growth chamber for 19 days under fertigation. The 30:70 mixture proved to be optimal in terms of crop performance, photosynthetic activity, intrinsic water use efficiency, and quality traits of lettuces. But, the 70:30 mixture was the best substrate in terms of pore-size distribution for water-plant relationship. By the cultivar comparison, the Red Salanova produced statistically higher dry biomass, leaf number, and area than Green Salanova; and showed the best performance in terms of quality traits, especially about phenolic content. With the idea of reducing inputs, the subsequent experiment assessed the nutritional supply of amendment. For this purpose, was involved one lettuce cultivar (Lactuca sativa L. cultivar ‘Grand Rapids’), grown on different substrates consisting of MMS-1 or LHS-1 simulants mixed with monogastric manure at varying rates (100:0, 90:10, 70:30, 50:50, w/w), for 30 days in an open-gas-exchange climate chamber with no fertilization. Specifically, we evaluated the lettuce growth on these substrates, the plant physiology and nutrient uptake, the microbial biomass C and N, enzymatic activity and nutrient bioavailability in the mixtures after plant growth. A better agronomic performance, in terms of fresh biomass production and physiology, nutrient availability and enzymatic activity, was provided by substrates containing MMS-1, in comparison to LHS-1-based ones. Amendment with a monogastric-based manure significantly improved the ability of both simulants to sustain plant growth. The best crop growth response was achieved on the 70:30 simulant/manure mixture. Our findings indicate that the addition of manure at specific rates (30%) may increase the biomass production of lettuce plants cultivated in MMS-1 simulant. In addition, considering the importance of supplementation of bioactive compounds in astronauts' diets. Was also evaluated how the substrates can modulate some qualitative traits as the organic acids, carotenoids content, antioxidant activity, and phenolic profile. The phytochemical composition is variably affected by manure addition, depending on the simulant. Indeed, was recorded an increment in lutein and β-carotene content by +181% and +263%, respectively, when applying the highest percentage of manure (50%) compared with pure simulants. The 50:50 MMS-1/manure treatment contained the highest amounts of individual and total organic acids. While the highest antioxidant activity (ABTS assay) was recorded when no manure was added. Matching crop growth performance and chemical, mineralogical, and physical-hydraulic characteristics of possible plant growth media for space farming allows a better understanding of the processes and dynamics occurring in the experimental substrate/plant system, potentially suitable for an extra-terrestrial BLSS. Therefore, the agronomic practice of amendment showed promising results. However, it must be tested with other species to verify its applicability in space colonies for food production purposes; or in combination with other factors such as fertilization rates or biostimulants application to reduce the stressors and allow better plants performance

Bioassays for evaluation of sanitary risks from food crops cultivated in potentially contaminated sites

Environmental pollution in agricultural contexts cannot be neglected since food crops can be an important exposure pathway for soil pollutants. In Italy the Law on the Environment (Law Decree 152/2006) is unclear with regard to agricultural areas, since the specific regulation provided for in Art. 241 has not been enacted. Current risk analysis is based only on direct risk (i.e. via ingestion and inhalation of soil particles), while indirect risk via food consumption is not considered. For defining potential risks for consumers, assessment of exposure to potentially toxic elements (PTEs) can be made through the analysis of their content in food crops and the estimation of the related hazard quotient (HQ) based on the ratio between PTE intake through food and the health risks due to PTE doses during a lifetime. In order to obtain a precautionary estimate, the worst case approach was followed by selecting species well known for their PTE accumulation capacity, such as chicory (Cichorium intybus L.), lettuce (Lactuca sativa L.), spinach (Spinacia oleracea L.), radish (Raphanus sativus L.) and rocket salad (Eruca vesicaria L.), and by cultivating these plants in hotspots with the highest PTE concentrations. The PTE contents in such crops show wide variability, with values from 0.005 to 0.054 mg kg–1 for arsenic (As), from 0.004 to 3.9 mg kg–1 for cadmium (Cd), from 0.17 to 0.79 mg kg–1 for chromium (Cr), from 0.22 to 1.18 mg kg–1 for copper (Cu), from 0.03 to 0.43 mg kg–1 for lead (Pb) and from 1.43 to 25.06 mg kg–1 for zinc (Zn). Lead and Cd contents in vegetables exceeded thresholds established by EC Reg. 1881/2006 in 14% and 25% of samples, respectively. By contrast, from HQ analysis, any potential risk of dietary exposure due to ingestion of As, Cr, Cu, Pb or Zn was excluded. Only Cd content in lettuce, spinach and chicory resulted in a potential health risk due to intake of such foodstuffs. The proposed method could resolve the lacuna in current Italian legislation regarding the evaluation of risks for human health due to the intake of contaminants through the food chain

Assisted phytoremediation for restoring soil fertility in contaminated and degraded land

The results of experiments carried out in the National Interest Priority Site (NIPS) Agro Aversano-Litorale Domizio in Campania (southern Italy) within the framework of the project ECOREMED (LIFE11 ENV/IT/275) are used as a basis for reporting the main threats to soil fertility. In this paper we focus on soil degradation and contamination due to illegal waste disposal and burning, widespread phenomena in the NIPS in question, evaluating different options for soil remediation with agriculturebased techniques in light of their impact on the ecosystem services of soils. Bioremediation and assisted phytoremediation are recognized as the best options for protecting human health and enhancing environmental quality, maintaining agricultural soil functions with the application of relatively low-cost protocols. The purpose of agriculture-based remediation techniques is threefold: i) make the area in question safe, interrupting exposure to contaminant pathways through ecological structures such as dense reed plantations or dense turfgrass combined with high-density tree rows for reducing ground wind speed; ii) remediation, aiming to reduce the bioavailable fraction of potentially toxic elements (PTEs); iii) environmental restoration, to improve environment and landscape quality of degraded, but not contaminated land. The technical steps for carrying out phytoremediation projects and the results of their application are described for the following case studies monitored in Campania: i) agricultural soil contaminated by bioavailable Cd (San Giuseppiello site in Giugliano); ii) industrial soil heavily contaminated by Pb and Cd (Ecobat site in Marcianise); iii) agricultural soils potentially contaminated by non-bioavailable PTEs and organic pollutants (Giugliano and Trentola-Ducenta sites); iv) physically degraded soil (Teverola site). In all the case studies phytoremediation proved a low-cost tool to reduce risks for human health and enhance environmental quality, whilst maintaining soil fertility and improving ecosystem services

Soil versus plant as indicators of agroecosystem pollution by potentially toxic elements

The major route of potentially toxic elements (PTEs) to humans is the intake through food. They enter the food chain principally by plants uptake from the soil and, to a less extent, through foliar deposition. The soil-to-plant transfer as part of the biogeochemical cycle of these elements is a complex and hardly predictable process. In this study, we investigated the capability of soils and plants to indicate PTEs inputs in an intermingled urban-rural landscape of south Italy affected by legal and illegal waste disposal and dumping. For this aim, 172 agricultural soil and plant (edible part) samples were collected in pairs from 47 municipalities and analyzed for 12 PTEs (As, Be, Cd, Co, Cu, Cr, Ni, Pb, Se, Tl, V, Zn). Soil extractions with 1 M NH4NO3 and 0.05 M EDTA pH 7 were applied to assess PTEs bioavailability. Results were examined according to plant species and main soil chemical properties. For Pb and Cd, the soil-to-plant transfer factors (TF) and the corresponding soil benchmark concentrations were also investigated. Zinc, Cu, Cd, and Pb were the only PTEs of anthropic origin severely polluting from 10 to 16% of the soils, but only in a very few cases exceeded physiological or EU legal critical values in the edible part of the plants. An evaluation of human risk due to the ingestion of these elements was tried; no risk for consumers for Zn, Cu, and Pb, while for Cd three values slightly exceeded the tolerable daily intake. Therefore, we conclude that crops cultivated in the studied area could represent only a moderate risk for human health. No correlation was found between soil and plant data, which likely highlights different pollution inputs. A large variability characterized the Pb and Cd TF, making it difficult to establish a unique benchmark concentration for the studied agricultural soils

Sweet Basil Functional Quality as Shaped by Genotype and Macronutrient Concentration Reciprocal Action

Basil (Ocimum basilicum L.) is among the most widespread aromatic plants due to its versatility of use and its beneficial health properties. This aromatic plant thrives in hydroponics, which is a valid tool to improve the production and functional quality of crops, but nevertheless, it offers the possibility to de-seasonalize production. A floating raft system was adopted to test the production and quality potential during autumn season of three different genotypes of Genovese basil (Aroma 2, Eleonora and Italiano Classico) grown in three nutrient solutions with crescent electrical conductivity (EC: 1, 2 and 3 dS m−1). The aromatic and phenolic profiles were determined by GC/MS and HPLC analysis, respectively. The combination Aroma 2 and the EC 2 dS m−1 resulted in the highest production, both in terms of fresh weight and dry biomass. The 2 dS m−1 treatment determined the major phenolic content, 44%, compared to the other two EC. Italiano Classico showed a higher total polyphenolic content in addition to a different aromatic profile compared to the other cultivars, characterized by a higher percentage of Eucalyptol (+37%) and Eugenol (+107%) and a lower percentage of linalool (−44%). Correct management of the nutritional solution combined with adequate genetic material managed an improvement in the production and the obtainment of the desired aromatic and phenolic profiles